The use of cyclic organometallic molecules as single-source MOCVD precursors is illustrated by means of examples taken from our recent work on SiC and AlN deposition, with particular focus on SiC. Molecules containing (SiC)2 and (AlN)3 rings as the “core structure” were employed as the source materials for these studies. The organoaluminum amide, [Me2AlNH2]3, was used as the AlN source and has been studied in a molecular beam sampling apparatus in order to determine the gas phase species present in a hot-wall CVD reactor environment. In the case of SiC CVD, a series of disilacyclobutanes, [Si(XX′)CH2]2 (with X and X′ - H, CH3 , and CH2 SiH2CH3), were examined in a cold-wall, hot-stage CVD reactor in order to compare their relative reactivities and prospective utility as single-source CVD precursors. The parent compound, disilacyclobutane, [SiH2 CH2]2, was found to exhibit the lowest deposition temperature (ca. 670 °C) and to yield the highest purity SiC films. This precursor gave a highly textured, polycrystalline film on the Si(100) substrates (70% with a SiC<lll> orientation).

Copper oxide films were prepared by organometallic chemical vapor deposition of copper acetylacetonate in an oxygen-rich environment. The films were characterized by X-ray diffraction, Auger electron spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. At 360 °C, Cu2O films were formed for an oxygen pressure of 150 torr and a copper acetylacetonate vapor pressure of 0.2 torr). The Cu2O film was polycrystalline, but the orientation was primarily [111]. Differential scanning calorimetry indicated that O2 assists decomposition of the organometallic precursor during pyrolysis.

An examination of thermal chemical vapor deposit elemental composition by EDAX has been completed for material films grown from Cu(acac)2 and Cu(tmhd)2 (acac = pentane-2,4-dionate; tmhd = 2,2,6,6-tetramethylheptane-3,5-dionate), using both hydrous and anhydrous carrier gas steams each of reducing (H2), inert (H2), and oxidizing (O2) composition.

Chemical vapor deposition using tetra(allyl) tungsten and molybdenum precursors yielded amorphous tungsten and molybdenum carbide films on pyrex substrates. The films were characterized by Auger, ESCA, SEM, XRD and resistivity measurements. Volatile pyrolysis products consisted primarily of propene, C3H6.

Several borane cluster compounds, such as pentaborane(9) and their corresponding metal complexes have been investigated in our laboratory for their utility as unique source materials for synthesizing metal/metal boride thin films by MOCVD. In this paper we report the preparation of thin films of nickel boride from the thermal decomposition of nido- pentaborane( 9) in the presence of anhydrous nickel chloride [NiCl2] in the vapor phase. Crystalline nickel boride thin films of controlled composition ranging from 0.1 to several microns have been readily prepared by controlling the temperature and the flow rate of the pentaborane(9) into the reaction chamber. The nickel boride films on GaAs were thermally annealed to form the Ni7B3 phase as hexagonal crystals in a Ni3B matrix. These films have been characterized by AA, AES, EDXA, SEM, XRD and electron diffraction. The phases were determined primarily by X-ray and electron diffraction experiments.

The possibility of growing tungsten nitride thin films from (tBuN)2W(NHtBu)2, a single-source molecular precursor with two nitrogen to tungsten double bonds, by low pressure chemical vapor deposition (LPCVD) was investigated. Deposition of thin films on silicon and glass substrates was carried out at temperatures 500 – 650 °C in a cold-wall reactor while the precursor was vaporized at 60 – 100 °C. Elemental composition of the thin films, studied by wavelength dispersive spectroscopy (WDS), is best described as WNx (x = 0.8 – 1.8). Elemental distribution within the films, studied by Auger depth profiling, is uniform. X-ray diffraction (XRD) studies show that the films have a cubic structure with a lattice parameter a = 4.14 – 4.18 Å. A stoichiometric WN thin film has a lattice parameter a equal to 4.154 Å. Volatile products, trapped at −196°C, were analyzed by nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC-MS). Isobutylene, acetonitrile, hydrogen cyanide and ammonia were detected in the condensable mixtures.

Excellent quality ZrO2 thin films were successfully deposited on single crystal silicon wafers by metalorganic chemical vapor deposition (MOCVD) at reduced pressures using tetrakis(2,2,6,6—tetramethyl—3,5—heptanedionato) zirconium, [Zr(thd)4]. For substrate temperatures below 530°C, the film deposition rates were very small (≤ 1 nm/min). The film deposition rates were significantly affected by: (1) source temperature, (2) substrate temperature, and (3) total pressure. As—deposited films are stoichiometric (Zr/O = 1/2) and carbon free. Furthermore, only the tetragonal ZrO2 phase was identified in as—deposited films. The tetragonal phase transformed progressively into the monoclinic phase as the films were subjected to high temperature post—deposition annealing. The optical properties of the ZrO2 thin films as a function of wavelength, in the range of 200 nm to 2000 nm, are reported. The measured value of the dielectric constant of the as—deposited ZrO2 films is around 19 in the frequency range of 5 kHz to 1000 kHz.

Ta2O5 and Nb2O5 films were deposited using the Lam Research Integrity™ reactor. The chemical precursors used were pentaethoxides of Ta and Nb. Typical films were deposited at a rate of 4 nm/min with uniformities of <1.5% lσ in the presence of O2 at 470°C. Annealing the Ta2O5 films did not change the O/Ta ratio. Annealing the Nb2O5 films increased the O/Nb ratio to 2.5/1 at 850°C. Interfacial SiO2 grew to 4 nm after annealing at 850°C for both Ta2O5 and Nb2O5. The as-deposited films were amorphous, but became crystalline above 600°C and 700°C for the Nb2O5 and Ta2O5 films respectively. The TEM observations on crystallization is supported by x-ray diffraction data.

This paper reviews the status of diamond heteroepitaxy approached by chemical vapor deposition and by physical methods. Reported are experiments with cubic boron nitride and nickel conducted with the help of microwave plasma chemical vapor deposition. X-ray diffraction data confirm diamond heteroepitaxy on the (111) faces of cubic boron nitride crystals. Heteroepitaxy on nickel was not demonstrated yet nevertheless suppression of graphite nucleation was achieved by formation of nickel hydride.

A nonequilibrium plasma jet has been used to deposit diamond films on a number of substrates, including silicon, silicon nitride, alumina, and molybdenum. Hydrogen is passed through a glow discharge and expanded through a supersonic nozzle to produce a highly nonequilibrium jet. Methane is added downstream of the nozzle, where it mixes and reacts with the nonequilibrium concentration of hydrogen atoms. The resulting supersonic jet strikes the substrate surface producing a high quality (determined by laser Raman spectrometry) adherent diamond film. Because of the low jet temperature, substrate cooling is unnecessary. Diamond deposition rates have exceeded 2 mg/kWh and I μm/h averaged over 16 cm2 area; good quality films prepared at substrate temperatures below 600 K. have been

Polycrystalline diamond films have been deposited on (100) silicon wafers by plasma enhanced chemical vapor deposition (PECVD) using a 1.5 kW microwave source to dissociate dilute gas mixtures of CH4 and O2 in H2. Films as thick as 20μm covering a 2″ diameter area were deposited at 925 °C, 40 Torr total pressure, and 500 sccm total flow. These have been characterized as a function of CH4 [0.2–4%] and Os [0–3%] concentrations by measurements of deposition rate, stress, surface roughness, morphology, and impurity levels (C-H and amorphous-graphitic carbon). Addition of oxygen to the discharge tends to reduce impurity levels in the diamond films; however, this is accompanied by a reduction in deposition rate. When an effective CH4 concentration [= %CH4 - %O2] is used as a metric for O2 -containing feed compositions, deposition rates as well as film properties are found to agree well with those obtained in the absence of O2. Thus, 1% CH4 in hydrogen is nearly equivalent to 4% CH4, 3% O2 in hydrogen as feed compositions for depositing diamond.

We have deposited diamondlike carbon (DLC) films on a variety of substrates from 250° C and higher. The effects of deposition temperature on the properties of DLC films deposited by a conventional laser ablation technique are compared with that of a unique laser-plasma deposition scheme. The calculated values of neff, the effective number of valence electrons, suggest that, with the increase in the deposition temperature, the diamondlike component (sp3 bonds) remains invariant for the laser deposited samples, and increases for the laser-plasma deposited films. Raman measurements show that the Raman allowed ‘G’ band upshifts to ˜1600 cm−1 for both deposition schemes. However, the disorder induced 'D' band remains invariant at ˜1370 cm−2 for the laser ablated samples, and downshifts to ˜1350 cm−1 for the laser-plasma deposited samples. These results suggest a correlation between the diamondlike content (sp3 bonds) and the Raman shift of the ‘D’ band.